White House press secretary Jen Psaki on Thursday defended the Biden administration’s efforts to ramp up at-home coronavirus testing amid a nationwide shortage of tests.

Psaki said that President Biden took steps following the emergence of the delta variant over the summer to expand COVID-19 testing capacity, including a $3 billion investment in at-home testing capacity.

Psaki said that Biden’s efforts early on helped lay the groundwork for the U.S. to purchase 500 million at-home tests to distribute to Americans beginning next year amid the rise of the omicron coronavirus variant.

“The president knew that we needed to increase testing capacity. That’s why he used the Defense Production Act to expand the supply of at-home tests. Without that, we wouldn’t have the supply in the market,” Psaki told reporters.

The Biden administration has come under some criticism for the testing shortage. Americans have struggled to get access to tests before the holidays and testing sites are seeing large volumes of people seeking COVID-19 tests.

Biden’s announcement Tuesday that the federal government would purchase 500 million tests to send to Americans free of charge represented a significant step, but the tests are not expected to be ready for delivery until January. The White House also needs to work through additional details on the plans, including determining how many each American can request.

During an ABC News interview on Wednesday, Biden said the testing shortage was not a failure of his administration but expressed some regret for the circumstances. Biden said he wished he “had thought about ordering half a billion” tests “two months ago.”

Psaki argued Thursday that the administration has been working to ramp up the testing supply since the summer, noting that testing companies began laying people off because of a lack of demand before the delta variant emerged and that the market needed to be built back up.

“When we saw a surge in demand in delta, we took additional actions to expand the over the counter test market” Psaki said, adding that the steps the administration took quadrupled the testing capacity over four months.

Psaki also made a point to note that the testing shortage is affecting other countries, not just the U.S.

“This is not just happening in the United States. This is happening all around the world where there is not enough testing capacity and we have taken steps that are more significant than any country in the world so that we have the testing needed to meet what people are looking for,” Psaki said.